Question

Lack of oxygen in muscles often leads to cramps among cricketers. This result is due to

• A. Conversion of pyruvate to ethanol
• B. Conversion of pyruvate to glucose
• C. Non conversion of glucose to pyruvate
• D. Conversion of pyruvate to lactic acid

Answer 1

The correct option is D Conversion of pyruvate to lactic acid

Hint: Intracellular acidosis occurs due to lactic acid accumulation and it has been regarded as the most important cause of skeletal muscle fatigue.

• Part 1 - Definition
• Anaerobic means without air (an means without).
• Anaerobic respiration is the partial breakdown of glucose into acid or alcohol along with carbon dioxide, in the absence of oxygen.

Part 2 - Anaerobic respiration in muscles

• During vigorous exercise, our heart and lungs could not get sufficient oxygen for our muscles in order for them to respire aerobically.
• In this case, muscles carry out anaerobic respiration.
• In this process, glucose is partially oxidized to pyruvate, which further converts forming lactic acids in muscles.
• The reaction proceeds as follows:-

$Glucose$ $\to$ $Pyruvate$ $\to$ $Lactic$ $acid$ + $Energy$

Part 3 - Location

• Anaerobic respiration is divided into two parts: glycolysis and fermentation.
• Both occur in the cytoplasm of a muscle cell.

Part 4 - Accumulation of lactic acid in muscles

• Lactic acid is formed and accumulated in the muscle under conditions of high energy demand, rapid fluctuations of the energy requirement, and insufficient supply of oxygen.
  
• Increasing acidity from the accumulated lactic acid and lack of energy cause cramps.
  

Part 4 - Conclusion

• Usually, the pyruvate formed from the glycolysis enters the Kreb's cycle as acetyl coenzyme A in the mitochondrial matrix and generates a pool of chemical energy (ATP, NADH and FADH).
• ​One of the alternate fates of pyruvic acid in cellular respiration is that it can be converted into lactic acid in the absence of oxygen in muscles and cause muscle fatigue.

Final step: Lack of oxygen in muscles often leads to cramps among cricketers due to the conversion of pyruvate to lactic acid.